1. Field of the Invention
This invention relates to ducts, and in particular to attaching flange portions to duct members for interconnecting duct members.
2. Description of the Related Art
Ducts and duct work are formed by securely interconnecting duct members and other components such as flanges using fasteners. Various arrangements have been suggested to facilitate the joining. Example devices and methods for such interconnections are shown in U.S. Pat. Nos. 4,288,115; 4,564,227; 4,725,083; 5,103,872; and 5,621,956. In general, they do not most advantageously address issues inherent with material handling, part manipulation, and the ease of assembly, particularly given the often difficult orientation of assembler to workpiece encountered in the installation of a ductwork system. The present invention overcomes these deficiencies by the use of a pre-selected array of depressions or openings in the flanges which permit ready joining.
U.S. Pat. No. 4,288,115 to Sullivan describes a duct jointing system with hollow flange members on the ends of ducts, and having a snap-on cleat for fastening abutting flange members together. A corner portion is shown to have holes in legs, but such holes do not receiving fastener.
U.S. Pat. No. 4,564,227 to Murck provides a flanged duct joint with snap-in corner pieces having legs which fit into two abutting flanges to assemble the flanges in a joined configuration.
U.S. Pat. No. 4,725,083 to Schauer discloses a flanged joint having walls on flanges shaped for receiving corner pieces. The abutting flanges are joined together by bolting complementary bores in the corner pieces. Depressions in the flange walls are oriented to receive complementary projections from the corner pieces in a friction fit, but the depressions are not and cannot be used to fasten complementary flanges together, since walls of the flanges are interposed between the depressions of the abutting flange walls.
U.S. Pat. No. 5,103,872 to Jyh-Long discloses a flanged joint with abutting flanges retained together by flange clamps and by bolts fastening corner pieces together. The flange strip elements have projections for engaging raised projections on the end portions of the ducts, but not the abutting flange.
U.S. Pat. No. 5,621,956 to Kolesar has flange members with screws inserted for attaching the flange members to the ends of ducts. Bolts pass through bolt holes in the corner pieces attached to the flanges for fastening abutting corner pieces and thus assembling the flanges and duct sections.
As noted, these prior art teachings present complicated arrangements for securing flanges to the ends of ducts and/or for interconnecting duct members, and such arrangements typically require additional components which make the interconnections more expensive to implement.
Another prior art method for interconnecting duct members, which is being commercially practiced, is shown in FIGS. 1-6, in which multiple layers of sheet metal are placed in juxtaposition, and apertures are created through which joining members are secured. As illustrated, a flange 10 is placed adjacent to an end portion 12 of a duct member. The flange 10 includes at least one wall member 14. The flange 10 includes a pair of wall members 14, 16 joined by an intermediate member 18, with the wall members 14, 16 placed on the duct member such that each wall member 14, 16 is adjacent to opposite sides of the end portion 12.
To secure the flange 10 to the duct member, a fastener 20 is placed adjacent to one of the wall members 14, 16, preferably the wall member adjacent to the exterior surface of the duct member, such as the wall member 14 shown in FIG. 2. A tool 22, such as a drill, or alternatively a repeater tool or gun, is used to provide pressure and optionally a drilling force to the fastener 20 in the direction of the arrow shown in FIG. 2, in order to create apertures 24 in both the flange 10 and the end portion 12 of the duct member, as shown in FIG. 3. In one embodiment, the fastener 20 may be a screw for serving both as a tool workpiece to create the apertures 24 and to function as the inserted fastener 20 after insertion by the tool 22.
In the fastened configuration of FIGS. 3-4, the fastener 20 passes through the apertures 24 to secure the flange to the duct member in the assembled configuration, allowing the flange 10 to join other flanges or components, such that the duct member connected to the flange 10 is positioned and assembled to other duct members, as required.
Although extensively used, this prior art insertion method has numerous disadvantages. For example, by requiring the fastener 20 to pass through multiple solid layers of material; that is, the wall members 14, 16 as well as the end portion 12, each formed of sheet metal, the assembler using the tool 22 must apply significant pressure to the fastener 20 to pierce three layers of metallic material. In addition, if the tool 22 is a drill or other device for applying a rotational force as well as a longitudinal insertion force in the direction of the arrow in FIG. 4, the assembler will experience significantly higher counter-torque as the fastener 20 passes through multiple layers 12-16 of material. These higher pressures and torques reduce the efficiency of insertion of the fastener 20 to join the flange 10 to the duct member, and may also cause injury to the assembler.
Furthermore, as the fastener 20 passes through the flange 10 and the end portion 12, debris at the insertion point from the formed apertures will be positioned between the flange 10 and the end portion 12. Thus, the assembled flange 10 and the end portion 12 often does not have a very tight fit in the final assembly.
Moreover, it is not uncommon that the insertion pressure applied to the fastener 20 typically causes one wall member of the flange and/or the portion of the duct member to bend away from the direction of insertion, and so causing push-out of the components from their original shape, as shown in FIGS. 5-6. The improperly pushed-out, or alternatively pushed in, and bent flange 26 has an outer wall member 28 and a push-out wall member 30 joined at a bend 32, with the distorted shape of the flange 26 caused by the force of the fastener 20 conveying the insertion pressure from the tool 22, in the direction of the arrow as shown in FIG. 2, to the wall member 30.
Once such push-out or bending occurs and forms the bent flange 26 shown in FIGS. 5-6, the fastener 20 must be removed for re-insertion into the flange 26, and the bent wall members 28, 30 of the flange 26 must be restored to their original shape as shown in FIGS. 1-2, or otherwise wastefully discarded and replaced with a new flange 10 and/or a new fastener 20, in order to provide a properly assembled and secure connection as shown in FIGS. 3-4. Otherwise, the joined flange and duct end assembly shown in FIGS. 5-6 will not be sufficiently secured, and may even be unsecured and thus useless for properly interconnecting ducts ends and components.
Remedying such bending, or in anticipation of bending, pre-clamping the assembly, increases the time to properly assemble the flanges to the duct members, and delays completion of the work. In addition, the inaccuracy and uncertainty of properly inserting the fastener 20 into the flange 26 and end portion 12 increases the chances for injuries due to the need for the duct assembler to manually stabilize both sides of the flange with one's hand near to the insertion point of the fastener 20, while the tool 20 applies the insertion pressure to the fastener 20.
There therefore exists a need exists for a simple and efficient method for securely mounting flanges to duct ends.